This invention relates generally to gas generation and, more particularly, to gas generation via chlorine-containing gas generant compositions which produce or result in gaseous effluents substantially free of hydrogen chloride.
It is well known to protect a vehicle occupant using a cushion or bag, e.g., an “airbag cushion” that is inflated or expanded with a gas when a vehicle experiences a sudden deceleration, such as in the event of a collision. Such airbag restraint systems normally include: one or more airbag cushions, housed in an uninflated and folded condition to minimize space requirements; one or more crash sensors mounted on or to the frame or body of the vehicle to detect sudden deceleration of the vehicle; an activation system electronically triggered by the crash sensors; and an inflator device that produces or supplies a gas to inflate the airbag cushion. In the event of a sudden deceleration of the vehicle, the crash sensors trigger the activation system which in turn triggers the inflator device which begins to inflate the airbag cushion, typically, in a matter of milliseconds.
Many types of inflator devices have been disclosed in the art for inflating one or more inflatable restraint system airbag cushions. Inflator devices which form or produce inflation gas via the combustion of a gas generating pyrotechnic material, e.g., a “gas generant,” are well known. For example, inflator devices that use the high temperature combustion products, including additional gas products, generated by the burning of the gas generant to supplement stored and pressurized gas to inflate one or more airbag cushions are known. In other known inflator devices, the combustion products generated by burning the gas generant may be the sole or substantially sole source for the inflation gas used to inflate the airbag cushion. Typically, such inflator devices include a filter to remove dust or particulate matter formed during the combustion of a gas generant composition from the inflation gas to limit or prevent occupant exposure to undesirable and/or toxic combustion byproducts.
In view of an increased focus on passenger safety and injury prevention, many automotive vehicles typically include several inflatable restraint systems, each including one or more inflator devices. For example, a vehicle may include a driver airbag, a passenger airbag, one or more seat belt pretensioners, one or more knee bolsters, and/or one or more inflatable belts, each with an associated inflator device, to protect the driver and passengers from frontal crashes. The vehicle may also include one or more head/thorax cushions, thorax cushions, and/or curtains, each with at least one associated inflator device, to protect the driver and passengers from side impact crashes. Generally, the gaseous effluent or inflation gas produced by all of the inflator devices within a particular vehicle, when taken as whole, are required to not include more than 5 parts per million hydrogen chloride in order to meet current industry safety guidelines. Thus, it is desired that the gas generant compositions used in such inflator devices produce as little hydrogen chloride as possible.
A number of gas generant compositions are known that include ammonium perchlorate as an oxidizer. Ammonium perchlorate is typically employed in gas generant compositions as a source of oxygen which promotes efficient combustion of the gas generant composition, e.g., complete conversion of carbon to carbon dioxide (CO2), hydrogen to water (H2O) and nitrogen to nitrogen gas (N2). Ammonium perchlorate, however, commonly also produces hydrogen chloride as a gaseous byproduct of combustion which, in too large a concentration, may be both toxic and corrosive. Hydrogen chloride gas can be “scavenged” or removed from the combustion gas stream by including a scavenger compound such as an alkali or alkaline earth metal nitrate such as sodium or potassium nitrate in the pyrotechnic gas generant composition. Such alkali or alkaline earth metal nitrates react with the hydrogen chloride to produce less or nontoxic alkali or alkaline earth metal chlorides such as sodium or potassium chloride. Such alkali or alkaline earth metal chlorides may, however, undesirably form as fine particulate matter or dust which can escape the inflator device. Additionally, the inclusion of ammonium perchlorate typically increases the combustion temperature of a pyrotechnic gas generant composition often resulting in increased levels of undesirable and potentially toxic effluent gases such as ammonia and carbon monoxide.
In view of the above, there is a need and a demand for pyrotechnic gas generant compositions that take advantage of the increased heat and oxygen provided by utilizing ammonium perchlorate as an oxidizer without undesirably increasing undesired gaseous and particulate combustion byproducts in the inflation gas stream. More particularly, there is a need and a demand for gas generant compositions that permit or facilitate the inclusion of chlorine-containing components or materials such as by either or both: 1) providing or resulting in a chlorine-containing effluent material, such as a relatively easily filterable metal chloride, such as can be effectively and efficiently removed from the gas stream within the inflator and 2) inhibit the formation of carbon monoxide and ammonia gases. There is a further need and a demand for gas generant compositions that provide improved gas yields and burn rates.